Field of the Invention
The present invention relates to development apparatus for handling developer material particles in electrostatographic reproduction machines such as copiers and printers. More particularly, the present invention relates to a self-sealing journal assembly for use in such a development apparatus for preventing detrimental developer material particle leakage from such apparatus.
In electrostatographic reproduction machines such as copiers and printers, it is well known to use development apparatus which handle developer material particles for developing latent images formed therein. Typically such a development apparatus has a developer material particle transport auger for example that includes a rotatable load shaft. Directly or by means of an extension unit, such a load shaft usually extends from the inside of a housing for the development apparatus to the outside thereof, where it is journaled through a bore in a bearing.
In order for the journal bearing to function properly and reliably, some form of a clearance gap is normally required between the outside diameter of the journaled shaft and the inner surface of the bearing bore in order to allow radial and axial motion of the shaft. Unfortunately however, the presence of such a required clearance gap ordinarily results in leakage of some of the developer material particles into the bearing assembly where they can detrimentally affect the proper function of the journal bearing.
As disclosed for example in U.S. Pat. No. 4,824,423 issued Jun. 27, 1989 to Anil G. Bhagwat, various sealing mechanisms have been proposed for sealing around such a shaft so as to prevent leaking of developer material from the development apparatus housing, and in order to protect the shaft-to-bearing intersurface area against damage by leaking particles.
Unfortunately however, such proposed mechanisms utilize sealed rolling elements and/or compressible sealing elements such as felt or rubber. Sealed rolling elements ordinarily are relatively expensive, require lubrication, and do not normally allow for such axial compliance. Felt and rubber sealing materials on the other hand are ordinarily incapable of compensating for deviations in axial location between shaft and bearing surfaces. In addition, the use of such felt and rubber sealing materials often involves undesirable wear and friction requirements matching problems due to differences between shaft, seal and bearing materials. Furthermore seals made from such materials normally also tend to degrade with time, particularly in an environment such as that in which developer material consisting of toner and magnetic carrier particles is being handled.